1. Field of the Invention
The present invention relates to an armature winding of a rotating-electric machine for use in engine starter and the like.
2. Description of the Related Art
In a dc motor with brush according to a prior art, lap winding and wave winding have been employed as a method for winding an armature. In case of wave winding, it is required to satisfy the expression of (kxc2x11)/p=integer (where: k is number of segments, 2p is number of poles), and the armature winding becomes either short-pitch winding or long-pitch winding.
Generally, it has been said that short-pitch winding is favorable in view of rectification. However, if short-pitch degree xcex4(xcex4=|Ns/2pxe2x88x92yb|, where: yb is a back pitch, Ns is number of slots) is set up to be excessively large, a commutating zone becomes broad, which is not favorable in view of rectification. Therefore, it is more preferable to select xcex4 as small as possible.
FIG. 6 is a winding diagram of an armature winding according to a prior art. In the drawing, reference numeral 21 is a commutator segment, numeral 22 is an armature coil, numeral 23 is a tooth of the armature, and numeral 24 is a slot.
As shown in FIG. 6, for example, in case of 2p=6 and Ns=23, Ns/2p=3.83. For the above reason, when inserting the armature coils 22 into the slots number 1 to 5 and establishing a back pitch yb as 4, a long-pitch winding of xcex4=0.17 is obtained.
Since the conventional rotating-electric machine is arranged as mentioned above, a problem exists in that when employing the long-pitch winding, inductance of the armature coil increases and output is reduced.
The present invention was made to solve the above-discussed problem, and has an object of providing a rotating-electric machine capable of improving output by reducing inductance of the coil.
A rotating-electric machine according to the invention includes an armature provided inside a stator, and an armature winding inserted into a slot provided in the armature, and in which the armature winding is formed into a wave winding and a short-pitch winding, and when putting short-pitch degree as xcex4, an expression of 0.5 less than xcex4 less than 1 is satisfied.
As a result of employing such an arrangement, inductance of a coil is reduced and output is improved.
Another rotating-electric machine according to the invention includes a stator composed of permanent magnet, an armature provided inside of the stator, and an armature winding inserted into a slot provided in the armature, and in which the armature winding is formed into a wave winding and a short-pitch winding, and when putting short-pitch degree as xcex4, an expression of 0.5 less than xcex4 less than 1 is satisfied.
As a result of employing such an arrangement, when a large current is applied to the armature winding, reduction in magnetic force of the permanent magnet of the stator due to armature reaction is difficult to occur.